Rick Santorum is coming under much closer — and more skeptical — scrutiny since he jumped to the top of Republican presidential polls this month, according to a computer-assisted analysis of social media data.

For the first time, politically engaged users of Twitter and Facebook are buzzing about Santorum more than about any other Republican candidate.

Santorum, a former senator from Pennsylvania, swept Republican voting in Minnesota, Missouri and Colorado on Feb. 7. Although all three contests were essentially beauty contests, with little official impact on the delegate count, Santorum's victories revived his campaign.

Before Feb. 7, Santorum was generally running third behind former Massachusetts Gov. Mitt Romney and former House Speaker Newt Gingrich of Georgia in most major national polls. Following those contests, he soared to the top of the major national polls, and he has remained there since.

Santorum's rise has been mirrored on social media, according to msnbc.com's analysis of nearly 2.2 million posts on Twitter and Facebook this month. And as the spotlight has focused on him, it has drawn opponents of his sharp-edged positions out of the shadows.

msnbc.com research/M. Alex Johnson; Crimson Hexagon Inc.

Click the image for the full-size chart.

Comparison of total numbers of opinions expressed about the Republican candidates the week before the Feb. 7 contests and this week. Former Massachusetts Gov. Mitt Romney is represented by the purple line. Former Sen. Rick Santorum of Pennsylvania is represented by the orange line.

The analysis examined posts through Thursday about the four remaining major Republican candidates, filtering out straight news reports and neutral posts, such as tweets noting that a candidate would be making a campaign appearance. The resulting sample was 1.2 million tweets and Facebook posts that expressed clear support for or opposition to one of them.

In the week leading up to the Feb. 7 contests, those Facebook and Twitter users preferred to talk about Romney by a ratio of more than 6 to 1 over Santorum.

Beginning Feb. 8, however, Santorum has been the No. 1 topic of conversation. This week, more than two-fifths of every post expressing an opinion — 41 percent — were about Santorum, compared to 32 percent for Romney, 15 percent for Gingrich and 12 percent for Rep. Ron Paul of Texas.

(The analysis uses a tool called ForSight, a data platform developed by Crimson Hexagon Inc., which is used by many media and research organizations to gauge public opinion in new media, among them the Pew Research Center and ESPN. The results aren't a scientific reflection of national opinion. Instead, they're a broad look at what is being said by Americans who follow politics and are active on Facebook, Twitter or both.)

Nonpartisan research indicates that Republicans and Democrats use social networking sites in roughly equal proportions. The demographics have gradually been trending older and more conservative as the sites are adopted by a larger proportion of the American public, studies indicate.

The msnbc.com analysis suggests that while people are much more enthusiastic about talking about Santorum, they're not any more enthusiastic about the man himself. On Feb. 7, before results of the three contests were known, 42 percent of Santorum's comments were positive to 58 percent negative; Thursday, after a debate Wednesday night in Mesa, Ariz., where Santorum came under sustained attack from Romney and Paul, the breakdown was 38 percent to 62 percent.

Consistently, the largest driver of sentiment about Santorum is his strong stance against same-sex marriage, making up 18 percent of all opinions expressed about him and 28 percent of all negative sentiment this week — proportions that have remained remarkably consistent since June, when msnbc.com began collecting data.

In a Facebook post typical of the anti-Santorum commentary, Jay A. Small of Vancouver, Wash., wrote this week:

From Rick Santorum's website: "Marriage is, and has always been through human history, a union of a man and woman – and for a reason. These unions are special because they are the ones we all depend on to make new life and to connect those new lives to their mom and dad."

So, Mr. Santorum, your religion's typical intolerance must then also stand for banning marriage between couples who do not choose, or are not able to procreate.

But other issues are now emerging around which significant opposition is crystallizing. The sentiment that Santorum is "too conservative," particularly in the prominence of his religious views — previously just one of several scattered notions — has broken into double digits this month, rising to 13 percent of all commentary and 20 percent of all negative opinion, such as this tweet by an Alaskan woman who describes herself as a Christian "pro-life supporter":

Twitter.com

The picture is different for Romney, who (at least according to msnbc.com's analysis) has yet to give voters a clear reason to vote for or against him. That suggests his supporters could be swayed by other candidates — or that he still could galvanize support with clearly articulated positions.

'Most electable'?In fact, the No. 1 reason social media commentators give for supporting Romney — both this week and going all the way back to June — is their belief that he is the "most electable" Republican in the race, a sentiment that has driven 36 percent of all positive opinions this week:

Twitter.com

A quarter cite Romney's competence or leadership; no other issue even makes it into double digits.

Likewise, opposition to Romney is widely scattered. A quarter of those expressing negative opinions this week cited his wealth, with many suggesting that he is out of touch with the majority of Americans, as in this tweet from Michaele Swiderski, a Tennessee woman who describes herself as a Jesus-loving conservative:

Twitter.com

But 15 percent also expressed concern over his Mormon faith, another 15 percent thought he was too closely tied to corporate interests, and 14 percent pinned the RINO label on him — that is, "Republican In Name Only," or not truly conservative.

Even in Michigan — his native state, which holds an important primary Tuesday — the single most mentioned word in social media posts about Romney this week (after his own name) isn't any political issue or position.